OIDIUM OR POWDERY MILDEW OF THE VINE. 



Fungous Diseases of the Vine. California is peculiarly fortunate 

 in its freedom from most of the serious fungous vine diseases which 

 add so much to the expense and uncertainty of grape growing in most 

 countries. Peronospora, Black Rot, and Anthracnose are here quite 

 unknown. Of the four most serious fungous diseases which attack the 

 above-ground portions of the vine, these three are the most to be feared, 

 as they are not only capable, if neglected, of destroying the whole crop 

 of a vineyard, but require the utmost vigilance and much troublesome 

 treatment with winter washes and summer sprays to hold them in 

 check. Their absence makes quite unnecessary the swabbing of the 

 dormant vines with sulfate of iron and the spraying of the growing 

 vines with Bordeaux mixture which are adopted here by some vine- 

 yardists who have learned the practice in Europe or the Eastern States 

 where it is necessary. 



On the other hand, the remaining serious fungous disease Oidium 

 exists in all parts of California. From one point of view, this is the 

 most serious disease of the four, as, if uncontrolled, it is capable of 

 spreading more universally through the vineyards and of absolutely 

 destroying the crops in nearly all. From another point of view, it is 

 the least to be feared, as it is possible to control it completely, at least 

 fti most parts of California, by much simpler and less expensive meth- 

 ods than are needed for the others mentioned. 



Introduction of Oidium into Europe. With the exception of An- 

 thracnose, which is a native of Europe, all these diseases originated on 

 the wild vines of the Eastern and Central parts of the United States. 

 Peronospora and Black Rot are comparatively recent introductions 

 into Europe. The* former was observed for the first time in 1878, the 

 latter not until 1885. The Oidium was first noted in Europe about 

 1845, when an English gardener named Tucker found it in graperies 

 at Margate, near the mouth of the Thames. It was discovered two 

 years later in the hot-houses of Paris and Belgium. 



Severity of the Disease in Europe. From this time it spread rap- 

 idly, until by 1851 it had reached every grape-growing country of 

 Europe. The amount of injury done by the disease was enormous and 

 increased every year, reaching its maximum in France about 1854. In 



